Container with flexible bottom



Nov. 5, 1968 R. L- BLANCHARD CONTAINER WITH FLEXIBLE BOTTOM Filed March 24, 1967 2 Shets-Sheet 1 FIG.2

INVENTOR.

RICHARD LEWIS BLANCHAR D ATTORNEY Nov. 5, 1968 R. L. BLANCHARD 3,409,157

CONTAINER WITH FLEXIBLE BOTTOM I Filed March 24, 1967 2 sheets sheet 2 FIG.5

R CHARD uzwls BLA NCHAR 0 ATTORNEY INVENTOR.

United States Patent 3,409,167 CONTAINER WITH FLEXIBLE BOTTOM Richard Lewis Blanchard, Barrington, 11]., assignor to American Can Company, New York, N.Y., a corporafion of New Jersey Filed Mar. 24, 1967, Ser. No. 625,645 1 Claim. (Cl. 220-66) ABSTRACT OF THE DISCLOSURE Background of the invention After filling and sealing containers made of non-rigid materials ('eig," thermoplastic) with certain types of products (eig, motor oil), it'has been found that the sidewalls of the containers tend to panel or become deformed when the containers have been stored for a period of time. This deformation or paneling of the sidewall of the container results from a reduction of the pressure within the interior of the container. After the container has been filled and sealed, a small amount of air generally remains trapped Within the container. Upon being stored, the contents of the container may chemically react with constituents of the residual air. Such chemical reactions cause the total pressure within the container to drop, and as a result the sidewall of the container will flexinward or panel in order to compensate for this internal pressure drop. When this condition occurs, the container assumes an undesirable appearance, and will not adequately support another container that may have been stacked on top of it. In some cases, the container may be filled vvith a heated product which reduces in volume upon subsequent cooling and which thereby tends to reduce the internal pressure in the sealed container. Since the reduction in internal pressure cannot always be practically avoided, the present invention provides a novel container construction wherein the container base flexes in preference to the container walls.

Summary of the invention In a thermoplastic container having a sidewall and bottom wall, flexure means are provided at the outer circumferential portion of the bottom Wall, such flexure means including an annular head at the juncture between the sidewall and the bottom wall. The container sidewall is thicker than the flexure means whereby upon a limited reduced pressure in the container, for example, when the oxygen of the air therein is consumed upon reacting chemically with the contents, t-heflexure means are operable to allow the bottom wall to distend inwardly, in preference to the sidewall, to effect a maximum volumetric inward displace-, ment as the bottom vvall flexes at said flexure means starting at said outer annular bead.

Description of the drawings sealed 3,409,167 Patented Nov. 5, 1968 FIGURE 3 is a partial cross-sectional view taken along the line 3-3 in FIGURE 1 showing the construction of the base of the container when in an unflexed condition;

FIGURE 4 is a partial cros-sectional view taken along line 44 in FIGURE 2 showing the container base when in a partially flexed condition due to a reduction in pressure within the container;

FIGURE 5 is a partial cross-sectional view of another embodiment showing the base of a container when in an unflexed condition;

FIGURE 6 is a partial cross-sectional view of the container base of FIGURE 5 when in a partially flexed condition due to a reduction in pressure within the container;

FIGURE 7 is a partial cross-sectional view of a further embodiment showing the base of a container when in an unflexed condition;

FIGURE 8 is a partial cross-sectional view taken of the container base of FIGURE 7 when in a partially flexed condition due to a reduction in pressure within the coutainer.

Description of the prefered embodiments Referring to the drawings and in particular to FIGURE 1, a container 10 is filled with a fluid, for example, motor oil. After the container has been filled, the fluid attains the level 14 just below the top rim 16 of the container. The container is sealed by an end closure 17 which may be affixed in any suitable manner, for example, by a doubleseam, spin weld, or heat seal.

After the container has been filled and sealed with the end closure 17, it appears as shown in FIGURE 2. An air space exists between the surface 14 of the fluid and the internal surface of the end closure 17. This air space results from the condition that it is not practical or economically feasible to fill the container completely with fluid to eliminate all residual air spaces or voids. Since such containers are [generally filled on production lines through filling and processing machinery, complex and intricate mechanisms would be required to assure that each container is filled to the extent that no space 'within the container is left vacant of fluid.

In the normal course of storing the filled container, it has been found that certain constituents of the fluid may react chemically With the air within the container. Such chemical reactions of the fluid result in a reduction of internal pressure in thecontainer in that the reactions use up the oxygen from the residual air space, and the partial pressure, previously created by the oxygen, is no longer present and, consequently, the internal pressure in the container will be reduced. A similar result of reduced total internal pressure would prevail for chemical reactions between the fluid and any of the other constituents or gaseous components of the residual space. Further, if the container is initially filled with a heated product (e.g., heated oil to make it less viscous for filling), its subsequent coolin'g will tend to cause a reduction in the internal pressure.

With reduction of internal pressure, the atmosphere or surrounding environment acts upon the container to cause the sidewall of the container to buckle or panel. When the sidewall 20 of the container is thus deformed or paneled, various problems arise with respect to the storage of the containers. For example, it is not possible to stack any significant number of containers on top of one another in order to conserve storage space. This is so because when the sidewall 20 panels or becomes deformed, as a result of a reduction of the internal pressure, the top and bottom planes of the container are generally no longer parallel, thereby resulting in instability in the container stack. Another problem resulting from the deformed condition of the container is that it gives the container an undesirable appearance. Such deformed appearances of the containers often render the latter unmarketable, even though the contents of the container are 3 entirely usable and unaffected by the deformation of the sidewau."

The deformation or paneling of the sidewall of the container is prevented, in accordance with the present inven-' tion, through a novel construction of the bottom wall or base of the'container wherein flexure means in the bottom wall provide preferential flexure in the latter. FIGURE 3 shows one embodiment of the invention wherein the base or bottom wall 18 includes a flexure means 19 comprising an outer bead or convex portion 22 located at the juncture between the sidewall and the base 18. The fiexure means 19 further comprises a second bead or convexportion 24 along with the-indentation or concave portion 21 disposed therebetween. Adjacent to the head 24 is an indentation or concave portion 26 which runs into a central bottom portion 30. v

FIGURE 3 shows the natural condition of the con tainer while FIGURE 4 shows the container base 18 after the container has been filled and the contents have chemically reacted or other action has taken place to initially reduce the pressure within the container. Because of the irregular configuration of the flexure means 19 and the fact that the thickness t of the flexure means is less than the thickness T of the sidewall 20, such flexure means 19 will bend, in preference to the sidewall 20, to compensate for the pressure reduction. When this bending or flexure occurs, maximum volumetric displacement is effected as the bottom wall 18 flexes from a position starting at the outer annular bead 22. The flexure occurs at the beads 22 and 24, continuing through the intermediate indentation 21. The reason for this is that the irregular flexure means 19 is thinner than the sidewall 20 of the container, the numeral 31 indicating the transition from the thicker sidewall 20 to the thinner base 18. Thus, the outer bead 22 tends to roll or hinge inwardly, allowing the entire base 18 to be displaced toward the inside of the container to elfect a maximum volumetric, inward displacement when partial or limited vacuum is present therein. The degree of flexure of the various parts of the flexure means 19 will depend on the particular configuration, the thickness, and the type of material used. Since the central bottom portion is displaced rather than flexed, its thickness may be selected as found most desirable to obtain best results. It may, for example, be the same thickness or thicker than the flexure means 19.

Preferably, the height H of the outer bead 22 is the maximum allowable for its supporting function and is determined by the degree of thinning adjacent the bead 22, i.e., the ratio between the base thickness t and sidewall thickness T. Greater bead heights H allow more flex but render the bead 22 too soft (i.e., not of suflicient rigidity) for its supporting function. The angle K is preferably less than 60 degrees. The smaller that angle K is, the easier the base 18 can flex inwardly, however, opposing this is the fact that too small an angle K will offer less total displacement or inward distention for higher degrees of vacuum. Consequently, it is preferable that angle K be the maximum at which the base 18, due to its geometry, will effect a preferential flex inwardly prior to paneling of the sidewall.

Angle I may be within the range of 20-90 degrees. The larger angle keeps the radial distance from indentation 21 to indentation 26 to a minimum. This allows less material thickness between these portions and allows more flex due to a thinner section.

Another advantage of the outer bead 22 being of relatively weaker construction over a controlled height H, is that the height setting of the doubleseaming head for affixing the end closure 17 becomes less critical because the outer bead 22 acts as a cushion that flexes prior to buckling of the sidewall 20. If the bead 22 is relatively sturdy and too much pressure is applied on the container during doubleseaming, the sidewall 20 might collapse sufficieutly to Cause problems in obtaining satisfactory 4 doubleseaming and sealing of the end closure'20-to the container. As previously indicated, to facilitate the deformation 0 the base 18 of the container in preference to the sidewall 20 thereof, the material'thickness of the flexure means 19 is less than that of the sidewall 20. The base 18 is joined to the relatively heavier sidewall 20 through the transition indicated generally at 31. Thus, the container.

base 18 is designed so as to be deformable in preference to the sidewall 20; In this manner, any compensation for.

the reduction in pressurewithin the containeris accomplished through deformation of the container base =18 rather than of the sidewall 20.

The design of the container base is such -that.-it may flex inward through a range of positions. If the internal container pressure drops further than that corresponding,v to' the position shown in FIGURE-'4, the bottom wall 18,

may move orflex further inwardly. Accordingly, as the pressure within the container continues to drop, the base 18 of the'container flexes inward to-compensate for this.

The following indicates parameters of the construction shown in FIGURE 3.

v I Range I Ideal Width (W) of head 22, inch 0. 18-0. 25 0.20 Height; of bead 22, inch 0. 085-0. 12 0. 10 Angle K, degrees 20-60 30-45 Angle J, degrees 20-90 70-83 Angle N, degrees 15-60 20-30 FIGURE 5 shows another embodiment for the design and construction of a flexible base for the container 10. In this design, the flexure' means 29 in base 33 comprises an outer head or annular portion 32 joined to the sidewall 20, the head 32 joining an inner head 34 which, in turn, leads to an indentation 36. The latter terminates in the generally flat central portion 38. Prior to' being filled and when the container is in the undeformed' state, the container is supported on the inner bead 34 and, depending on the thickness and configuration, it might also be supported on the central portion 38. When the internal container pressure is initially reduced, the base 33 flexes; in an inward direction, to the position shown in FIG- URE 6'.

As in the case of the embodiment of FIGURE 3, the thickness 1 of the flexure means 29, including the outer bead 32, is less than the sidewall 20 thickness T of the container. Thus, the outer bead 32 allows the entire base 33 to be displaced toward the'inside of the container when the aforesaid initial partial vacuum is present therein, thereby to provide maximum volumetric displacement, with flexure occurring at the beads 32 and 34 as the portion therebetween tends to rotate about bead 32.

Assuming that thethickness of the sidewall 20 is within the range specified for the first embodiment of FIGURE 3 (i.e'., 0.02 to 0.04 inch), the material thickness of the flexure means 29 for the embodiment ,of FIGURE 5 preferably would reside within the range of 0.012 to 0.035 inch. The internal diameter of'the container for both of the embodiments of FIGURES 3 and 5 is nominally 4 inches, when associated with the preceding values.

In the embodiment of FIGURE 7, the base 41 is shaped intermediate between the two designs of FIGURES 3 and 5. An outer bead 40 of the fiexure means 43 is joined to the sidewall 20. In contrast with the outer bead 22 'in FIGURE 3, the outer bead 40 does not provide support for the unfilled container (FIGURE 7). Th'e'outer head 40 connects with an inner head 42 which, in turn, leads to indentation 44, the latter being joined to the central flat portion 48. y

In the initial stage of flexure, the central portion 48 is construction,

displaced inward to the position shown in FIGURE 8. In this initial stage of fiexure, the filled container is supported by the outer bead 40 and, depending on the thickness and configuration, it may also be supported on the inner bead 42.

Assuming that the thickness of the sidewall 20 is within the range specified in the first embodiment in FIGURE 3 (i.e., 0.02 to 0.04 inch), the material thickness of the flexure means 43 in the embodiment of FIGURE 7 preferably would reside within the range of 0.012 to 0.035 inch. The internal diameter of the container is nominally 4 inches when associated with the preceding values.

It is thought that the invention and many of its attendant advantages will be understood from the foregoing descriptions and it will be apparent that various changes may be made in the form, construction, and arrangement of the parts without departing from the spirit and scope of the invention or sacrificing all of its material advantages, the form hereinbefore described being merely a preferred embodiment thereof.

I claim:

1. A container body of thermoplastic material or the like having a sidewall and a bottom wall, said bottom wall having fiexure means at the outer annular portion thereof comprising a first annular bead disposed at the juncture between the container sidewall and the bottom wall and a second annular bead disposed radially inwardly of the said first bead, said flexure means further comprising an annular concave portion joining said annular beads, said bottom wall having a central portion joined to said second annular bead by a second annular concave portion, said first annular bead being thinner than the adjacent sidewall with the transition in thickness occuring substantially at the juncture between the sidewall and said first annular bead, said central bottom wall portionbeing displaced inwardly, in preference to the sidewall, upon a relative reduction of pressure in the container, as the flexure means flexes from a position starting at the first annular bead and continuing through said first annular concave portion and said second annular bead.

References Cited UNITED STATES PATENTS 2,982,440 5/ 1961 Harrison 220-66 3,105,765 10/1963 Creegan 220-66 X FOREIGN PATENTS 234,103 6/1961 Australia.

THERON E. CONDON, Primary Examiner. GEORGE E. LOWRANCE, Assistant Examiner. 

